596/2021 Thiemo Fetzer
Reliable COVID-19 testing remains a central pillar to manage the pandemic. Yet, the accuracy and reliability of tests and test equipment has regularly been brought into question. Both false-positive and false-negative test results convey costs. Yet, false negatives are likely more problematic due to the risk of onward transmission and the failure to break infection chains as a result. This paper studies the epidemiological impact of a false negative in the context of a high vaccine uptake country. Between 2 September and 12 October an estimated 43,000 PCR tests in the UK may have produced a false negative test result with individuals infected being told that they tested negative. These instances were particularly pronounced in the South West of England. Using a synthetic control method approach concentrating on the 13 most affected regions, this paper estimates that every false negative COVID-19 case is likely to have caused between 0.6 to 1.6 additional infections in the subsequent weeks.